The present invention relates to a stator assembly, and more particularly to a low-pressure compressor exit stator assembly which interfaces with a full hoop outer shroud pressure vessel within a gas turbine engine.
A gas turbine engine typically includes a rotor assembly which extends axially through the engine. A stator assembly is spaced radially from the rotor assembly and includes an engine case which circumscribes the rotor assembly. A flow path for working medium gases is defined within the case. The flow path extends generally axially between the stator assembly and the rotor assembly.
The rotor assembly includes arrays of rotor blades. The arrays of rotor blades extend radially outward across the working medium flow path in proximity with the case. Arrays of stator vane assemblies are interdergitated with the arrays of rotor blades. The stator vanes extend inward from the case across the working medium flow path into proximity with the rotor assembly to guide the working medium gases when discharged from the rotor blades.
An exit stator vane assembly typically includes a multiple of stator vanes, an outer case, and an inner case, which extend circumferentially about the working medium flow path. Conventional stator vane assemblies utilize a pierced aluminum outer shroud that receives the vane tip through the shroud and provide surface area for potting with a rubber compound. The rubber compound provides a seal between the flow path and an intermediate case core compartment area. The outer shroud is supported by the intermediate case at the rear and allowed to “float” radially through a bayonet attachment.
The material of the outer shroud typically differs from the stator vanes and attachment interfaces. The outer shroud is typically manufactured of aluminum for weight/cost and material compatibility with an aluminum bleed duct, whereas other stator assembly components are manufactured of titanium for increased strength. Titanium and aluminum have different thermal growths and the dimensional changes which result from temperature excursions during operation have to be absorbed at the outer shroud to bleed duct interface. That is, the outer shroud section bends or flexes to manage the level of stresses and contact loads through deflection. Although effective, conventional pierced shroud arrangements may not effectively withstand the high pressure and temperature environments in modern gas turbine engines over prolonged time periods.
Some outer shrouds are of a full hoop geometry to create an uninterrupted vessel which withstands the high pressure and temperature environments typical of advanced gas turbine engines. However, a full hoop design may be too stiff to permit conventional stress management through shroud flexibility. Mounting or a full hoop outer shroud have heretofore required relatively complicated attachment arrangements which limits full hoop outer shroud utilization to certain areas within the gas turbine engine.
Accordingly, it is desirable to provide a stator assembly with a full hoop outer shroud that satisfies the mounting, leakage, durability and thermally induced deflection requirements common to a gas turbine engine.